When the Following Redox Equation Is Balanced with Smallest Whole $\to$

When the following redox equation is balanced with smallest whole number coefficients, the coefficient for Sn(OH) ₃^- will be _____.
Bi(OH) ₃(s) + Sn(OH) ₃^-(aq) $\to$ Sn(OH) ₆^2-(aq) + Bi(s) (basic solution)

A) 1
B) 2
C) 3
D) 6
E) none of the above